Microchannel heat exchanger fin

ABSTRACT

A heat exchanger includes a plurality of tubes ( 12 ), each tube configured for a flow of fluid therethrough and one or more fins located between adjacent tubes of the plurality of tubes. The one or more fins are spaced by a fin pitch (Fp, 18 ) and are configured to improve thermal energy transfer between the plurality of tubes and ambient air. Each fin includes a fin face extending between the adjacent tubes, a substantially planar fin cap ( 22 ) connected to the fin face secured to one or the tubes, and a fin radius (Rc, 26 ) connecting the fin face to the fin cap such that the fin radius is reduced to promote condensate removal from the heat exchanger.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to heat exchangers. Morespecifically, the subject disclosure relates to fin and tubeconfigurations for microchannel heat exchangers.

Heating, ventilation, air conditioning and refrigeration (HVAC & R)systems include heat exchangers to reject or accept heat between therefrigerant circulating within the system and surroundings. One type ofthe heat exchanger that has become increasingly popular, due to itscompactness, structural rigidity and superior performance is amicrochannel or minichannel heat exchanger (MCHX) which includes two ormore containment forms, such as tubes, through which a cooling orheating fluid (such as refrigerant or glycol solution) is circulated.The tubes typically have a flattened cross-section and multiple parallelchannels. Fins are typically arranged to extend between the tubes to aidin the transfer of thermal energy between the cooling/heating fluid andthe surrounding environment. The fins have a corrugated pattern,incorporate louvers to boost heat transfer and are typically secured tothe tubes via brazing. Typical MCHX fin and tube arrangements, however,have the disadvantage of retaining large quantities of moisture, wateror condensate, within the fin and tube structure, due to their highcompactness and thus increased surface tension. The accumulated moistureaccelerates corrosion of the fin and tube structure which leads todecreased thermo-hydraulic performance or effectiveness of the heatexchanger and eventual failure of the heat exchanger when the tubes arecorroded sufficiently to be perforated, thus releasing thecooling/heating fluid. Further, along with retention of moisture, thetypical structure leads to the buildup of corrodant substances andmechanical stresses in the structure leading to stress corrosion whichfurther accelerates deterioration of the fin and tube structure andresultant failure of the heat exchanger. The art would well receive afin and tube structure which reduces the accumulation of moisture in theheat exchanger matrix thereby reducing corrosion of the heat exchanger.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, a heat exchanger includes aplurality of tubes, each tube configured for a flow of fluidtherethrough and one or more fins located between adjacent tubes of theplurality of tubes. The one or more fins are spaced by a fin pitch(F_(P)) and are configured to improve thermal energy transfer betweenthe plurality of tubes and ambient air. Each fin includes a fin faceextending between the adjacent tubes, a substantially planar fin capconnected to the fin face secured to one or the tubes, and a fin radius(R_(C)) connecting the fin face to the fin cap such that the fin radiusis minimized to promote removal of condensate from the heat exchanger.

According to another aspect of the invention, a heat exchanger includesa plurality of tubes, each tube configured for a flow of fluidtherethrough. One or more fins are located between adjacent tubes of theplurality of tubes. The one or more fins are spaced by a fin pitch(F_(P)) and are configured to improve thermal energy transfer betweenthe plurality of tubes and ambient air. Each fin includes a finextension extending beyond a tube width. The extended portion of the finis laterally flared and shaped to reduce capillary effects and enhancewater drainage.

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features, and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is cross-sectional view of an embodiment of a heat exchanger;

FIG. 2 is another cross-sectional view of an embodiment of a heatexchanger illustrating a fin face, fin cap, fin radius and louver of theheat exchanger;

FIG. 3 is a cross-sectional view of an embodiment of a heat exchangerillustrating a fin extension;

FIG. 4 is a cross-sectional view of an embodiment of a heat exchangerincluding multiple heat exchanger tubes;

FIG. 5 is a cross-sectional view of an embodiment of a heat exchangerincluding a fin notch;

FIG. 6 is a perspective view of an embodiment of a heat exchangerincluding a fin notch;

FIG. 7 is a perspective view of an embodiment of a slotted heatexchanger tube; and

FIG. 8 is a cross-sectional view of a welded slotted heat exchangertube.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

Shown in FIG. 1 is an embodiment of a tube and fin arrangement of a heatexchanger 10. The heat exchanger 10 includes a plurality of tubes 12.Each tube 12 in the embodiment shown includes multiple channels 14through which cooling fluid is circulated. In the embodiment of FIG. 1,each tube includes sixteen channels 14, but it is to be appreciated thatany number of channels 14 may be utilized. A plurality of fins 16 extendbetween the tubes 12 to aid in increasing heat transfer between thetubes 12 and the surrounding air. In some embodiments, the fins 16 aresecured to the tubes 12 by, for example, brazing, or other suitablemeans such as for instance soldering or gluing, and in some embodiments,the fins 16 may have a fin thickness (F_(TH)) of between about 50 andabout 100 microns. It is to be appreciated that the fin thickness ismerely exemplary, and other fin thicknesses outside of the describedrange may be utilized within the scope of the present disclosure. Theheat exchanger 10 of FIG. 1 is typically a horizontal tube heatexchanger of the type used in, for example, air conditioning condenserapplications. It is to be appreciated that other tube orientations arefeasible and within the scope of the invention.

Referring now to FIG. 2, the fins 16 are arranged along the tubes 12 andspaced from each other at a fin pitch (F_(P)) 18. The fins 16 of someembodiments are folded or corrugated fins 16. The fin 16 includes a finface 20 extending between the tubes 12 at a fin angle 74 which, in someembodiments, is nonperpendicular to the tubes 12, and a fin cap 22disposed at each end of the fin face 20 at the tubes 12 and extendingalong the tubes 12. The fin 16 is secured to the tubes 12 at the fin cap22. The fin cap 22 is substantially planar, and in some embodiments, thefin face 20 is also substantially planar.

Each fin face 20 includes a plurality of through openings, for example,louvers 24 arrayed along a lateral extent of the fin 16. The louvers 24improve heat transfer and also assist in reducing water retention in theheat exchanger by providing an alternate passage for moisture, water,and/or condensate to drain through the heat exchanger 10. A transitionbetween each fin cap 22 and fin face 20 is a fin radius (R_(C)) 26. Itis desired to reduce the fin radius 26 in order for a louver height(L_(H)) 28 to be increased relative to a fin height (F_(H)) 30, thusincreasing an overall size of the louver 24 opening within the fin 16.In some embodiments, a ratio of louver height 28 to fin height 30,L_(H)/F_(H), is between about 0.8 and about 0.95, and the preferredrange is between about 0.85 and about 0.92. Further, the fin radius 26relates to fin pitch 18 such that a ratio of fin radius 26 to fin pitch18, R_(C)/F_(P), is between about 0.1 and about 0.4. The preferred rangeof R_(C)/F_(P) is between about 0.2 and about 0.3

Referring now to FIG. 3, in some embodiments, a fin width (F_(W)) 32extends beyond a tube width 34 by an extension 36 at at least one tubeside 38, and in some embodiments, both tube sides 38. In someembodiments, the extension 36 extends laterally away from the tube side38 as well as transversely at least partially across a tube thickness40. The resulting extension 36 extends upwardly or downwardly in ahorizontal tube 12 heat exchanger 10, and may be substantially linear orplanar in profile, or in other embodiments may be substantially arcuate,a combination of linear and arcuate or other profile. As shown in FIG.3, the extension 36 may comprise two planar extension portions 74, andfurther, the extension 36 may have a substantially squared-offcross-section. It is to be appreciated, however, that the squared-offcross section is merely exemplary and other cross-sectional shapes arecontemplated within the scope of the present disclosure. Extending theextensions 36 upwardly or downwardly reduces surface tension effects andutilizes gravitational forces to encourage flow of condensate 42 awayfrom the tubes 12 thereby reducing corrosion of the tubes 12. To achievethe desired drainage, it is not required that an extension width (E_(W))44 be overly large relative to the overall fin width (F_(W)) 32. In someembodiments, a ratio of extension width 44 to fin width 32, E_(W)/F_(W),is between about 0.02 and about 0.1, while the preferred E_(W)/F_(W)range is between about 0.02 and about 0.04, to enhance the desireddrainage effect while minimizing the amount of space utilized by thefins 16 Likewise, a transverse component (E_(T)) 48 of the extension 36does not need to be overly great appreciable relative to the tubethickness (T_(T)) 40 to produce the desired effect. A ratio of thetransverse component 48 to the tube thickness 40, E_(T)/T_(T), isbetween about 0.05 and about 0.4, while the preferred E_(T)/T_(T) rangeis between about 0.05 and about 0.15. It is desired, however, that thetransverse component 48 be relatively large when compared to a finthickness (F_(T)) 50 (shown in FIG. 2). For example, in someembodiments, a ratio between the transverse component 48 and the finthickness 50, E_(T)/F_(T), is between about 1 and about 3, while thepreferred E_(T)/F_(T) range is between about 1.75 and about 2.5.Further, the transverse component 48 is related to the fin radius 26,such that a ratio of the transverse component 48 to the fin radius,E_(T)/R_(C), is between about 0.2 and about 2.

Referring now to FIG. 4, in some embodiments, each fin 16 spans two ormore tubes 12 located at each fin cap 22 with a gap (T_(G)) 52 betweenadjacent tubes 12. As shown in FIGS. 5 and 6, some embodiments include afin notch 54 substantially aligned with the tube gap 52. A relationshipexists between a tube pitch (T_(P)) 56, which is a distance betweentubes 12 located at opposing fin caps 22 and a notch height (N_(H)) 58of the fin notch 54. A ratio of the notch height 58 to the tube pitch56, N_(H)/(T_(P)−T_(T)) is about 0.15 to about 0.3. In some embodiments,N_(H)/(T_(P)−T_(T)) is about 0.1 to about 0.2 to encourage moisture flowoutward toward the extensions 36. Shown clearly in FIG. 6, each finnotch 54 has a notch width (N_(W)) 60 extending in a direction along thelength of the tube 12. The notch width 60 is sized relative to the finpitch 18, the fin height 30, and the tube pitch 56 in order to maximizethe gravitational effects and reduction in surface tension desired. Therelationship is expressed as follows:

N _(w)/(F _(P)−Sqrt(F _(H) ²−(T _(P) −T _(T))²)

In some embodiments, the relationship equals about 0.3 to about 0.9,while the preferred range of the relationship is about 0.4 to about 0.7.

Another embodiment is illustrated in FIG. 7. The embodiment of FIG. 7illustrates a tube 12 including a tube slot 62 extending therethrough.The tube slot 62 defines an additional egress location for moisture,condensate, and/or water from the heat exchanger 10. The slot 62 has aslot width (S_(W)) 66. A ratio of the slot width 66 to a tube width(T_(W)) 68, S_(W)/T_(W), is between about 0.05 and about 0.2 to providethe moisture egress while not significantly reducing an amount of fluidthe tube 12 is capable of carrying or effecting heat transfer andpressure drop characteristics of heat exchanger 10. The slot 62 has aslot length (S_(L)) 70 extending along a tube length (T_(L)) 72 of thetube 12. It is desired for the slot length 70 to be as large as possiblegiven the tube length 72, to spread its effect over the entire tubelength 72. Thus, a ratio of the slot length 70 to the tube length 72,S_(L)/T_(L), is between about 0.8 and about 0.95. As shown, the slottedtube 12 may include one or more refrigerant inlets 74 and one or morerefrigerant outlets 76, and may be connected to one or more coolantmanifolds 78 at either end of the tube length 72. The slotted tube 12may be formed one of many ways including extrusion of the slotted tube12. The slot 62 may be formed in a secondary operation by, for example,punching. Referring to FIG. 8, the slotted tube 12 may be formed bywelding of an inner sheet 80 and an outer sheet 82 to a corrugated sheet84 which forms dividers between adjacent coolant passages 86.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

1. A heat exchanger comprising: a plurality of tubes, each tubeconfigured for a flow of fluid therethrough; one or more fins disposedbetween adjacent tubes of the plurality of tubes, the one or more finsspaced by a fin pitch (F_(P)) and configured to improve thermal energytransfer between the plurality of tubes and ambient air, each finincluding: a fin face extending between the adjacent tubes; asubstantially planar fin cap connected to the fin face secured to one orthe tubes; and a fin radius (R_(C)) connecting the fin face to the fincap such R_(C) is reduced to promote condensate flow from the heatexchanger.
 2. The heat exchanger of claim 1 such that a ratio of the finradius to the fin pitch, R_(C)/F_(P), is between about 0.1 and about0.4.
 3. The heat exchanger of claim 2, wherein the ratio of the finradius to the fin pitch, R_(C)/F_(P), is between about 0.2 and about0.3.
 4. The heat exchanger of claim 1, wherein each fin face includesone or more louvers.
 5. The heat exchanger of claim 4, wherein a ratioof a louver height (L_(H)) to a fin height (F_(H)), L_(H)/F_(H), isbetween about 0.8 and about 0.95.
 6. The heat exchanger of claim 5,wherein L_(H)/F_(H), is between about 0.85 and about 0.92.
 7. The heatexchanger of claim 1, wherein each fin includes a fin extensionextending beyond a tube width.
 8. The heat exchanger of claim 7, whereinthe fin extension extends laterally beyond the tube width andtransversely at least partially across a tube thickness.
 9. The heatexchanger of claim 7, wherein the fin extension is configured to directmoisture accumulated in the fin structure away from the tubes.
 10. Theheat exchanger of claim 7, wherein a ratio of an extension width (E_(W))to a fin width (F_(W)), E_(W)/F_(W) is between about 0.02 and about 0.1.11. The heat exchanger of claim 10, wherein E_(W)/F_(W) is between about0.02 and about 0.04.
 12. The heat exchanger of claim 7, wherein a ratioof a transverse component (E_(T)) of the fin extension to a tubethickness (T_(T)), E_(T)/T_(T), is between about 0.05 and about 0.4. 13.The heat exchanger of claim 12, wherein E_(T)/T_(T) is between about0.05 and about 0.15.
 14. The heat exchanger of claim 7, wherein a ratioof a transverse component (E_(T)) of the fin extension to a finthickness (F_(T)), E_(T)/F_(T), is between about 1 and about
 3. 15. Theheat exchanger of claim 14, wherein E_(T)/F_(T), is between about 1.75and about 2.5.
 16. The heat exchanger of claim 7, wherein a ratio of atransverse component (E_(T)) of the fin extension to the fin radius,E_(T)/R_(C), is between about 0.2 and about
 2. 17. The heat exchanger ofclaim 1, wherein each fin of the one or more fins spans two or moretubes along a fin width.
 18. The heat exchanger of claim 17, whereineach fin includes a fin notch in the fin face disposed substantiallyaligned with a tube gap between two tubes of the two or more tubes. 19.The heat exchanger of claim 18, wherein a ratio of a notch height(N_(H)) to a tube pitch (T_(P)), N_(H)/T_(P), is between about 0.15 andabout 0.3.
 20. The heat exchanger of claim 19, wherein N_(H)/T_(P), isbetween about 0.1 and about 0.2.
 21. The heat exchanger of claim 1,wherein each tube of the plurality of tubes, includes a through slotextending along a length of the tube.
 22. The heat exchanger of claim21, wherein a ratio of a slot width (S_(W)) to a tube width (T_(W)),S_(W)/T_(W), is between about 0.05 and about 0.2.
 23. The heat exchangerof claim 21, wherein a ratio of slot length (S_(L)) to a tube length(T_(L)), S_(L)/T_(L), is between about 0.8 and about 0.95.
 24. A heatexchanger comprising: a plurality of tubes, each tube configured for aflow of fluid therethrough; one or more fins disposed between adjacenttubes of the plurality of tubes, the one or more fins spaced by a finpitch (Fp) and configured to improve thermal energy transfer between theplurality of tubes and ambient air, each fin including a fin extensionextending beyond a tube width.
 25. The heat exchanger of claim 24,wherein the fin extension is configured to direct moisture accumulatedin the fin structure away from the tubes.
 26. The heat exchanger ofclaim 24, wherein a ratio of an extension width (E_(W)) to a fin width(F_(W)), E_(W)/F_(W) is between about 0.02 and about 0.1.
 27. The heatexchanger of claim 26, wherein E_(W)/F_(W) is between about 0.02 andabout 0.04.
 28. The heat exchanger of claim 24, wherein a ratio of atransverse component (E_(T)) of the fin extension to a tube thickness(T_(T)), E_(T)/T_(T), is between about 0.05 and about 0.4.
 29. The heatexchanger of claim 28, wherein E_(T)/T_(T) is between about 0.05 andabout 0.15.
 30. The heat exchanger of claim 24, wherein a ratio of atransverse component (E_(T)) of the fin extension to a fin thickness(F_(T)), E_(T)/F_(T), is between about 1 and about
 3. 31. The heatexchanger of claim 30, wherein E_(T)/F_(T), is between about 1.75 andabout 2.5.
 32. The heat exchanger of claim 24, wherein each finincludes: a fin face extending between the adjacent tubes and; asubstantially planar fin cap connected to the fin face secured to one orthe tubes; and a fin radius (R_(C)) connecting the fin face to the fincap such that a ratio of the fin radius to the fin pitch, R_(C)/F_(P),is between about 0.1 and about 0.4.
 33. The heat exchanger of claim 32,wherein the ratio of the fin radius to the fin pitch, R_(C)/F_(P), isbetween about 0.2 and about 0.3.
 34. The heat exchanger of claim 32,wherein each fin face includes one or more louvers.
 35. The heatexchanger of claim 34, wherein a ratio of a louver height (L_(H)) to afin height (F_(H)), L_(H)/F_(H), is between about 0.8 and about 0.95.36. The heat exchanger of claim 35, wherein L_(H)/F_(H), is betweenabout 0.85 and about 0.92.